Class 47 generators

[Justin Smith]

I read that Class 47s had two different generators fitted, a Brush TM160 - 64 Mk4 and a TM172 - 50 Mk1.
Does anyone know the difference between them and which were fitted to which Locos ?
Thanks

 

[Magdalia]

I read that Class 47s had two different generators fitted, a Brush TM160 - 64 Mk4 and a TM172 - 50 Mk1.
Does anyone know the difference between them and which were fitted to which Locos ?
Thanks

It is a bit more complicated than that. As far as I can tell from the sources I have here:

D1500-19 (47401-420) 47-4aX had TG 160-60 (built at Loughborough)
D1520-49 (47001-016, 47421-434) 47-bX, 47-4bX and 47-4cX had TG 160-60 Mk2 (built at Loughborough)
D1550-74 (47017-019, 47435-454/529) 47-dX, 47-4dX and 47-4eX had TG 160-60 Mk4 (built at Crewe)

The rest had TG 172-50 Mk1.

The codes for generators were TG, the TM codes were traction motors.

 

[D365]

The codes for generators were TG, the TM codes were traction motors.

Thanks, I was reading the original post and got a bit confused! (admittedly I don't have any working experience of Class 47, it's Class 56 that is my area of expertise)

 

[ExRes]

I read that Class 47s had two different generators fitted, a Brush TM160 - 64 Mk4 and a TM172 - 50 Mk1.
Does anyone know the difference between them and which were fitted to which Locos ?
Thanks

Hopefully you'll be able to find the answers to all things 47 on the Class47.co.uk website

 

[norbitonflyer]

If they all had generators (and not alternators) why were only the first batch (1500-19 aka 47401-20) known as "Generators". was it something to do with them being fitted for ETH from new, whereas it was retro-fitted to later members?

 

[Magdalia]

A bit more on this. The difference is linked, though not in a straightforward way, to the wiring of the traction motors.

All of the locos with TG 160-60 generators are series parallel.
For the loco to be all parallel it has to have a TG 172-50 generator.

The complicated bit is that there were a small number of locos built at Loughborough that had the TG 172-50 generator but nevertheless were series parallel. These were D1682-1701 and D1707-14, later 47096-113 and 47119-124. The only ETH fitted locos in this batch were 47486 and 47487, which spent a while at Stratford and did not have a good reputation.

If they all had generators (and not alternators) why were only the first batch (1500-19 aka 47401-20) known as "Generators". was it something to do with them being fitted for ETH from new, whereas it was retro-fitted to later members?

That is down to the way that the ETH power is supplied. D1500-19 ETH was powered by a separate generator, the others had ETH powered by a dual wound alternator.

 

[Richard Scott]

There would be a difference as early 47s had motors wired as 3 series pairs in parallel whereas later ones were all parallel. The all parallel arrangement leads to higher output current but lower voltage from the generator than the series parallel arrangement.

 

[43096]

If they all had generators (and not alternators) why were only the first batch (1500-19 aka 47401-20) known as "Generators". was it something to do with them being fitted for ETH from new, whereas it was retro-fitted to later members?

It’s to do with the ETH: 47401-420 had ETH generators whereas all others with ETH have alternators.

 

[Justin Smith]

It is a bit more complicated than that. As far as I can tell from the sources I have here:

D1500-19 (47401-420) 47-4aX had TG 160-60 (built at Loughborough)
D1520-49 (47001-016, 47421-434) 47-bX, 47-4bX and 47-4cX had TG 160-60 Mk2 (built at Loughborough)
D1550-74 (47017-019, 47435-454/529) 47-dX, 47-4dX and 47-4eX had TG 160-60 Mk4 (built at Crewe)

The rest had TG 172-50 Mk1.

The codes for generators were TG, the TM codes were traction motors.

Thanks for that.
Are we saying the the choice of generator was nothing to do with if they were the "generator" 47s (the 47/4s), but if they had series of parallel traction motors ?

 

[Magdalia]

Are we saying the the choice of generator was nothing to do with if they were the "generator" 47s (the 47/4s), but if they had series of parallel traction motors ?

TG 160-60, TG 160-60 Mk2, TG 160-60 Mk4 and TG 172-50 Mk1 are main generators which provide the power for traction. Yes, upgrading the main generator to TG 172-50 Mk1 is what allows the traction motors to be all parallel. This is nothing to do with ETH.

The locos as built then had an auxiliary generator to provide power for things like compressors, exhausters and lighting.

What are colloquially called the Generators D1500-19/47401-420 had a third generator which provided power for ETH.

The ETH locos from 47421 upwards have a dual wound alternator, instead of the auxiliary generator. This provides power for the auxiliary circuits and the ETH at different voltages from each of the two windings.

 

[Richard Scott]

What are colloquially called the Generators D1500-19/47401-420 had a third generator which provided power for ETH.

The ETH locos from 47421 upwards have a dual wound alternator, instead of the auxiliary generator. This provides power for the auxiliary circuits and the ETH at different voltages from each of the two wiwindings.

I believe the third generator was a DC machine in the same vane as a 50? Also believe they had electric cooling fans, possibly also run off the same generator, also like a 50?
Later ETH machines were AC machines, which was rectified for auxiliary power and also train heat.

 

[43096]

I believe the third generator was a DC machine in the same vane as a 50?

Yes - hence @Magdalia using the terms generator (for a DC machine) and alternator (for AC).

 

[Magdalia]

I believe the third generator was a DC machine

Later ETH machines were AC machines

In the terminology that I'm using, generators produce direct current, alternators produce alternating current.

I'm not an electrical engineer, but my understanding is that dual wound alternators (in 47421 upwards) were a technological advance that weren't practical when D1500-19 were designed. Or maybe it just needed some lateral thinking to devise an arrangement with alternating current then rectified back to direct current?

 

[Richard Scott]

In the terminology that I'm using, generators produce direct current, alternators produce alternating current.

I'm not an electrical engineer, but my understanding is that dual wound alternators (in 47421 upwards) were a technological advance that weren't practical when D1500-19 were designed. Or maybe it just needed some lateral thinking to devise an arrangement with alternating current then rectified back to direct current?

That's correct terminology although often nowadays referred to as AC or DC generator.
Solid state electronics were in their infancy in early 1960s so likely reliable, compact rectifiers just weren't available. By early 70s technology had moved on, also expect the AVR (automatic voltage regulator) was changed for an electronic one in 47/4 conversions, which were required to control the auxiliary output? Know 45/1s had an electronic AVR but these weren't the most reliable of units.

 

[Magdalia]

Solid state electronics were in their infancy in early 1960s so likely reliable, compact rectifiers just weren't available.

Thanks, that sounds plausible. Didn't some of the early AC electric locos on the WCML have some technical issues with rectifiers?

also expect the AVR (automatic voltage regulator) was changed for an electronic one in 47/4 conversions

I'd be interested to know what happened with class 47 AVRs. The class 31 ETH conversions were in two batches: the early 1970s conversions (31401-424) had carbon pile AVRs but the the early 1980s conversions (31425-468) had electronic AVRs.

 

[Richard Scott]

Thanks, that sounds plausible. Didn't some of the early AC electric locos on the WCML have some technical issues with rectifiers?

Think some early ones were Mercury arc rectifiers but believe many retrofitted with solid state rectifiers at some point.

Yes - hence @Magdalia using the terms generator (for a DC machine) and alternator (for AC).

Yes, we've established that but modern terminology often refers to both as generators one being AC generator and one being a DC generator irrespective of the fact that traditionally DC machines were generators and AC machines alternators.

 

[Wyrleybart]

If they all had generators (and not alternators) why were only the first batch (1500-19 aka 47401-20) known as "Generators". was it something to do with them being fitted for ETH from new, whereas it was retro-fitted to later members?

The "generators" were actually quite distinct from the "normal" ETH 47s and this was noticable with the ETH switch on. The engine of a "normal" ETH 47s would run slightly faster than idle when producing therms. The "generator" also would, but when the power handle was moved to take power, the engine note momentarily died before spooling up, in the same way class 33s do. .

 

[ac6000cw]

Think some early ones were Mercury arc rectifiers but believe many retrofitted with solid state rectifiers at some point.

Classes 81-84 were built with mercury-arc rectifiers, all replaced by/during the 1970s with silicon diode rectifiers on the surviving locos. The first 30 class 85s were built with germanium diode rectifiers, the last 10 silicon diode rectifiers.

Mercury-arc rectifiers (containing a pool of liquid mercury) on a bouncing, swaying and vibrating loco were never a good idea, but they were the only sensible/feasible solution at the time the locos were designed.